Powdered husks of the psyllium seed are a common and effective bulk laxative. The hydrophilic properties of this natural fibrous laxative cause ingested doses to absorb large amounts of water, thus producing bulk and normalizing regularity through proper stool formation.
A single, normal adult dose of psyllium bulk laxative is about 3 grams of psyllium powder, dispersed by the user in water or in an aqueous beverage. However, powdered psyllium has very poor wetting capabilities and therefore must be vigorously mixed with aqueous fluids to produce a palatable dispersion.
Psyllium powder resists wetting in water or aqueous beverages because of its fine particle size and the inability of water to penetrate the powder mass due to fast surface hydration and swelling. Vigorous agitation of the psyllium powder in water results in a lumpy dispersion. The lumps, although wetted on their outer surface, contain dry undispersed powder on the inside. Fluid penetration must therefore precede hydration in order to accomplish instant wettability and dispersability.
A number of attempts have been made in the past to improve the usability of psyllium. U.S. Pat. No. 4,321,263, for example, describes coating granulated psyllium particles with an alcoholic solution of either polyethylene glycol or polyvinyl pyrrolidone and granulating the thus coated particles.
U.S. Pat. No. 4,588,589 teaches an antidiarrheal composition comprising bismuth subsalicylate and a polymeric hydroabsorptive agent selected from psyllium and glucomannan. The compositions may be prepared in a variety of forms which can be taken orally.
U.S. Pat. No. 4,666,716 is also directed to an antidiarrheal composition in which nonsteroidal anti-inflammatory drugs are combined with a polymeric hydroabsorptive agent such a psyllium in a variety of forms.
U.S. Pat. No. 3,922,339 describes coating of a medicant with a psyllium film.
U.S. Pat. No. 4,639,367 teaches a psyllium bulk laxative foam.
Currently, psyllium products are marketed in powder mixtures and chewable dosage form. As noted above, use of psyllium in a powdered form as a bulk laxative has posed some difficulty in mixing of the psyllium with water. As a result, a tablet dosage form for bulk laxative would be preferred. However, rapid and complete disintegration of the tablet is critical to the proper performance of psyllium. The tablet breakup and particle deaggregation must be maximized in order to improve the capability of psyllium to absorb and retain the moisture and act as a bulk providing medium.
A problem in making psyllium bulk laxative in tablet form is that psyllium is not compressible; it is very elastic with very minimal plastic deformation. In addition, compressed tablets must be able to withstand the process involved in tablet coating and packaging without crumbling. At the same time, improperly formulated tablets will not disintegrate into particles, thereby inhibiting the swelling of psyllium into gel.
Accordingly, it is an object of the present invention to provide a psyllium tablet that is sufficiently compressable to be manufactured, disintegrates easily in water and yet is not fragile during shipment.